linux-kernel - Re: Kconfig: ARCH=x86 causes wrong utsname.machine

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Message-ID: <473E209A.7080806@zytor.com>
Date:	Fri, 16 Nov 2007 14:58:34 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	Andreas Herrmann <aherrman@...or.de>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Kconfig: ARCH=x86 causes wrong utsname.machine

Sam Ravnborg wrote:
> On Fri, Nov 16, 2007 at 07:20:15AM -0800, H. Peter Anvin wrote:
>> Andreas Herrmann wrote:
>>> The new ARCH=x86 kernel build causes weired machine strings on 32-bit.
>>> For a cross-compiled kernel I have
>>>
>>> 	 $ uname -m
>>> 	 x66_64
>>>
>>> For a kernel natively built on a 32 bit machine I have
>>>
>>> 	$ uname -m  
>>> 	x66
>>>
>>> Looking at the sources, I think that utsname->machine was initially
>>> set as "x86_64" and "x86", respectively.
>>> But in arch/x86/kernel/cpu/bugs.c in check_bugs() the second character
>>> is set to '6' on my K7.
>>>
>>> I think the right solution for that problem is to use "x86_64" as the
>>> machine name for 64-bit and to keep the old "i[3456]86" strings for
>>> 32-bit kernels.
>> Absolutely.  This would be userspace-visible ABI breakage.
> 
> Any good suggestions here???
> UTS_MACHINE is set in top-level Makefile and if we specify
> make ARCH=x86
> we do not know if i386 or x86_&4 is correct until the configuration
> has been read.
> 
> Should we report a "make ARCH=x86" as uname -m == x86??
> 

That would break 5 years of a stable ABI.  I don't think that is even 
remotely feasible.

	-hpa
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